Visual behavior of human infants in the first half year of life will be studied. The long-term goal of the project is to understand how the infant develops and uses a stable and reliable cognitive model of his world. Experiments will include studies of the physical characteristics of visual stimuli that influene visual behavior, of the development of peripheral vision, of the development of form perception, and the development of early social response. Infrared corneal-reflection photography will provide a detailed record of where on a visual display an infant fixates during scanning. Eye-movement data will be supplemented by data on changes in heart rate, pupil diameter, and in some experiments, sucking. Such data will allow study of how the infant organizes his perceptions into higher-order structures, and of visual mechanisms mediating social development in early infancy. The research may provide the basis for a new tool for assessing intellectual-developmental functioning in infancy, and it may clarify existing data on the eye movements of older children and adults. Finally, data from early infancy have theoretical implications for the issue of whether perception is learned or innate.